1. Technical Field of the Invention
The invention relates to optical systems and elements. More specifically, the invention relates to an optical beamsplitter that can be used to propagate optical signals.
2. Description of the Related Art
A beamsplitter is an optical device that receives an incident light beam and divides it into two components. The first component is propagated from the beamsplitter as a transmitted beam. The second component is propagated as a reflected beam, angularly displaced with respect to the transmitted beam.
A conventional beamsplitter comprises a cube of optically-transparent material that encases a thin layer of semi-reflecting material oriented diagonally across its interior. Approximately one-half of the light entering one face of the beamsplitter is reflected by the semi-reflecting material through an adjacent face as a reflected light beam. The remaining portion of the light from the incident light is transmitted by the layer of semi-reflecting material through the opposite face as a transmitted light beam.
Beamsplitters are used in optical devices such as in scanners, interferometers and back-scattering detectors for measuring back-scatter from a particle system. One problem associated with conventional cubic beamsplitters is distortion caused by light striking beamsplitter faces at oblique, i.e. non-perpendicular, angles. The transmission through the beamsplitter is refracted according to Fresnel's Equations. The resulting light beam is parallel to the incident beam but displaced from it. The amount of displacement depends on the angle of incidence and the index of refraction of the optical materials used in the beamsplitter. This distortion can be compensated for, to some extent, by repositioning system components.
U.S. Pat. No. 6,414,797 to Gorden Videen discloses a Beamsplitter Prism with Spherical Faces for Transmitting or Reflecting Spherical Waves Without Magnification.